Water deficit stress applied only or combined with salinity affects physiological parameters and antioxidant capacity in Sesuvium portulacastrum

Abstract

Sesuvium portulacastrum is a promising halophyte well adapted to salt and to drought. However, no information in the literature was available about its antioxidant capacity. The objective of this study is to investigate the effects of water deficit applied alone or combined with salinity on some physiological parameters, proline and polyphenol accumulation, and antioxidant and antiradical activities. Seedlings were cultivated under optimal or limiting water supply (respectively, 100% and 25% of field capacity, FC). The amount of the evapotranspirated water was replaced by a nutrient solution containing either 0 or 200mM NaCl. Water deficit stress reduced plant growth together with a significant decline in leaf water content. Salinity mitigated the deleterious effects of water deficit stress on growth and led to an increase in net CO2 assimilation and stomatal conductance. In addition, salt supply under water deficit significantly increased leaf proline concentration and reduced lipid membrane peroxidation, assessed by leaf malondialdehyde concentration. Phenolic compound content increased significantly when plants were transferred from water deficit stress to 100% FC. However, plants subjected to water deficit stress combined to salt had high polyphenol content and the highest level of the antiradical activity in their stems. As a whole, cultivating S. portulacastrum under water deficit stress combined with salinity might be an interesting approach to exploit antioxidant metabolites from this species for medicinal and industrial purposes.Recovery of most of the studied parameters was substantial following relief of stress. Drought stress alone or combined with salinity did not cause permanent alterations in S. portulacastrum plants, which conserve their growth potentialities, and which can be a useful species in re-vegetation programs in arid saline areas.